Refrigeration devices including refrigeration cycles are widely used for household purposes or business purposes, as home electric freezers/refrigerators, air conditioners, show cases, and others. The refrigeration devices include sealed compressors for compressing a refrigerant gas. Also, it is known that air compressors for use in industries are the sealed compressors. In recent years, there has been an increasing demand for global environment conservation. Under the circumstances, there has been a strong demand for the high efficiency of the sealed compressors. Further, a demand for reduction of a noise has been increasing.
Conventionally, to realize the higher efficiency of the sealed compressor and the reduction of the noise in the sealed compressor, a technique in which a plurality of discharge holes are provided to discharge the refrigerant gas from a compression chamber. For example, as shown in FIG. 7, Patent Literature 1 discloses a valve plate 550A provided with two discharge outlets 551a, 551b (discharge holes) and one suction inlet 555. The discharge outlets 551a, 551b are equal in diameter. Trepanning seal sections 554a, 554b (valve seat seal sections) which are different in diameter are provided around the discharge outlets 551a, 551b, respectively. These discharge outlets 551 are covered by valve reeds (discharge valves), respectively, which are not shown.
In this configuration, the two discharge outlets 551a, 551b which are equal in diameter can increase the total area of the discharge holes. This makes it possible to reduce a resistance generated when the refrigerant gas is discharged from the interior of a compression chamber through the discharge outlets 551. Therefore, the excess compression loss of the discharged refrigerant gas can be reduced. As a result, the high efficiency of the sealed compressor can be realized.
A force applied by the refrigerant gas to push up the valve reeds is proportional to the area of the trepanning seal sections 554a, 554b. Since the trepanning seal sections 554a, 554b are different in diameter from each other, this causes a difference between the push-up forces in the discharge outlets 551a, 551b which are equal in diameter. This also causes a difference between the timings when the valve reeds start to open, and hence a difference between the timings when the valve reeds are closed. Due to the differences, the valve reeds collide against the corresponding trepanning seal sections 554a, 554b at different timings, and thus the impact forces generated due to the collision of the valve reeds against the corresponding trepanning seal sections 554a, 554b can be reduced in magnitude. As a result, a noise can be mitigated.
As shown in FIG. 8, Patent Literature 2 discloses a valve plate 550B provided with two discharge holes 551c, 551d. The valve plate 550B is provided with discharge valve reeds (not shown) on a surface thereof which is away from a compression chamber 534. The tip end surface of a piston 560 (end surface which is closer to the valve plate 550B) is provided with projections 561c, 561d to correspond in position to the discharge holes 551c, 551d, respectively. As shown in FIG. 8, when the piston 560 is located at a top dead center, the two discharge holes 551c, 551d are closed by the two projections 561c, 561d, respectively.
In this configuration, since the projections 561c, 561d move into the discharge holes 551c, 551d, respectively, it becomes possible to prevent a situation in which the refrigerant gas remains inside of the discharge holes 551c, 551d. Therefore, during a suction stroke, the re-expansion of the remaining refrigerant gas can be suppressed, and the volumetric efficiency can be increased. As a result, the efficiency of the sealed compressor can be increased.